Air cushion for shock absorption

ABSTRACT

An air cushion for shock absorption according to the present invention, comprises a flexible and elastic foam material capable of restoring an air cell thereof to its original shape and size under a static pressure transformable by an impact force, a cover made of a soft non-porous material for closely enclosing the foam material in the inside thereof, a discharge valve formed in the cover for discharging an air in the inside of the air cell of the foam material to the atmosphere when the air cell is subject to the shock, and one or more intake valve formed in the cover separately from the discharge valve for intaking the atmosphere to the air cell when the air cell is restored to its original size and shape after impacted. When shocked or restored, the shock can be efficiently absorbed by selectively operating the discharge valve and intake valve and differing their volumes from each other. Thus, the articles, for example notebook computer, which are easily broken and damaged in performance, can be more perfectly protected by the air cushion.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to an air cushion for shock absorption, and more particularly to an air cushion for shock absorption, which improves its dynamic resistance to a shock by selectively controlling air intake and discharge when shocked.

[0003] 2. Description of the Related Art

[0004] In general, articles easily broken or damaged when shocked, i.e., personal computer, printer machine, electronic equipment, communication system, products made of glass, plastic, ceramic, etc., are embedded in a properly designed packing case or carrying case to prevent any damage to them when loaded, transported, carried, and used.

[0005] One of the above articles easily damaged by a shock is a portable computer, generally called a laptop computer or notebook computer. It is well known that the notebook computer includes easily impacted components, such as a LCD Panel, a hard disc drive, a plastic case, a variety of electronic equipments, and diverse connectors, etc. Thus, the packing case or carrying case should be made surely absorbing the shock. In the case where a user carries the carrying case containing a notebook computer therein to use the notebook computer during a trip, when he transports the carrying case with his hands or with a strap of the carrying case hung on his shoulder, the carrying case is high from the surface of the land. If he accidentally drops the carrying case, the notebook computer may be seriously damaged.

[0006] The impact force applied to an article by a dropping is increased based on the acceleration of gravity (G) expressed as 32 feet/sec². For example, dropping of a notebook computer weighing 6 pounds (lb) from a height of 24 inches produces an impact force in excess of 300 pounds, which is more than 50 times as much as the previous 6 pounds because of the acceleration of gravity (G).

[0007] U.S. Pat. Nos. 5,217,119 and 5,524,754 disclose a carrying case including specific buffering means. That is, the carrying case is provided with an elastic sling suspension system. The suspension system absorbs a shock by supporting the notebook computer to its position above the bottom of the case by means of an elastic sling. Accordingly, when the notebook computer drops, the suspension system absorbs the shock by virtue of the spring effect of the elastic sling. The suspension system, however, is structurally complicated and costly. Therefore, they are actually used for limited purposes and users, for example, when a variety of machineries including a printer machine, etc., are required to be carried together in a carrying case, or a carrying case allowing the notebook computer to be executed in a state of being housed therewithin is required to be used.

[0008] In addition, U.S. Pat. Nos. 4,339,039 and 5,139,838 as well as Korean Utility Model Registration No. 183638 disclose air pads of a relatively simple structure contained in a packing container or a carrying case, wherein easily impacted articles like a notebook computer or the like are protected within the air pads.

[0009] Among them, Korean Utility Model Registration No. 183638 and U.S. Pat. No. 4,339,039 more related to the present invention will be described herein below. They all provide air pads formed by sealing a plastic foam therein, which are designed to enclose and hold surroundings of an easily impacted article including a notebook computer, etc., within a carrying case or a packing case, thereby absorbing any shock to the article.

[0010] First, Korean Utility Model Registration No. 183638 employs a structure provided with a plurality of air pads as fundamental notions, wherein Lair under a specific pressure and with a foam material are filled between an outer coat and an inner coat which are to be fusion spliced to each other. Since the air and the foam material are filled between the outer coat and inner coat and then the conventional outer and inner coats are fusion spliced to be completely sealed to each other, the air present on an air cell in the foam material can not be released, lessening a buffering effect. In other words, the volume of the air cell becomes decreased due to the impact force when shocked, and the air and the foam material lose their shapes to reduce the shock. In that case, if the outer and inner coats are sealed, the reduced volume of the air cell would be small, thereby slightly reducing the impact force. Further, if a positive pressure inside the air pads is excessively high, the air pads are forced to have a negative pressure by themselves, rarely achieving the shock absorption.

[0011] In the meantime, U.S. Pat. No. 4,339,039 provides a foam cushion installed inside a packing container to protect easily impacted articles, including electronic equipments, from being damaged during a transportation. One of figures illustrating the foam cushion is selected and drawn in the attached FIG. 1. Referring to FIG. 1, the foam cushion is structurally characterized in that a compressible foam material 2, such as a flexible foam, is sealed in the inside of a soft non-porous cover 3 and a plurality of air vents 4 are formed in a lateral side of the cover 3. This is because the inside of the cover 3 is in communication with the atmosphere through the air vents 4. If a cushion 1 is shocked, the cover 3 and the foam material 2 are compressed so as for the air inside to be discharged to the atmosphere through the air vents 4, resulting in an attenuation of the shock. The compressed cover 3 and the foam material 2 are restored by an air intake through the air vents 4.

[0012] Further, FIG. 2 to FIG. 4 are showing another conventional air cushion similar to the air cushion of FIG. 1. Referring to FIG. 2 to FIG. 4, an air cushion is applicable to a carrying case 5 for transporting a note book computer 6. The air cushion 10 seals a flexible foam material 11 to the inside of a non-porous cover 12 and is provided with a plurality of air vents 13 in communication between the atmosphere and the inside of the cover 12, similarly in FIG. 1. If impacted, therefore, the cover 12 and the foam material 11 are compressed and the air inside is discharged through the air vents to the atmosphere, resulting in an attenuation of the impact. The compressed cover 12 and the foam material 11 are restored when an air enters through the air vents 13. In FIGS. 2 to 4, a support plate member 14 supports the air cushion when it is installed, and a suture 15 stitches the air cushion 10 onto the support plate member 14.

[0013] The above two air cushions employ air vents to intake and discharge the air, which show more improved shock absorption effect than the completely closed cushion of Korean Utility Model Registration No. 183638 but can not actively react to the shock since all the air intake and discharge are carried out by means of only the air vents. For instance, dropping is accompanied with a series of rapid movements. That is, after there happens a first impact where an article drops and halts, it bounces and then drops again. It repeats this until it completely stops. Such a drastic acceleration followed by a drastic deceleration in an opposite direction and a deceleration cycle (bounding) causes consecutive latent damages to the easily impacted article after the first shock. The above described two air cushions achieve the air intake and discharge through the air vents. Thus, if a gross cross sectional area of the air vent is very small, the air intake through the air vent is slowly carried out and shape restoration of the flexible foam is delayed, failing to cope with the consecutive impacts after the first impact. Since a relatively small force for the flexible foam itself is needed in its shape restoration if compared to when it is shocked, the restoration force for the flexible foam suffers a loss due to a frictional resistance of the air when it is passed through the narrow orifice of the air vent. Contrarily, if the gross cross sectional area of the air vent is very large, the flexible foam can be restored immediately to a sufficient size to absorb the consecutive shocks since it has little air resistance. However, the internal air is excessively released in a very short time through the large cross section of the air vent when first shocked, the flexible foam is excessively transformed without a huge resistance, and the shock absorption cannot be efficiently carried out, thereby increasing the possibility of damaging the article. Besides, although the flexible foam is restored in a relatively short time after the first impact, it is apt to be transformed by the consecutive shocks, thereby reducing the consequent effect after the prompt restoration. As a result, the plastic foam should be, disadvantageously, made of a hard material so as to have a static force requirement much greater than the minimum static force requirement needed to support the weight of the flexible foam in the static condition. Once the flexible foam is made hard, it has a very weak point in absorbing less impact force, even though it efficiently absorbs greater impact force.

[0014] Finally, when the air vent is commonly used to intake and discharge the air, it is almost impossible to maintain the air efflux when impacted and the influx when restored to the optimum level. Accordingly, either effect among them should be ignored, or both effects should be ignored to some extent.

SUMMARY OF THE INVENTION

[0015] It is, therefore, an object of the present invention to provide an air cushion for shock absorption, which can efficiently absorb a shock by installing a discharge valve system for discharging an air and an intake valve system for intaking the atmosphere and by selectively controlling the air communication with the atmosphere when shocked and restored.

[0016] It is another object of the present invention to provide an air cushion for shock absorption, which can realize a dynamic limit to the air volume ventilated in the discharge valve system to quickly respond to the air discharge velocity through the discharge valve system in accordance with the increase of the shock, and realize the intake valve system of a low velocity and high volume to promptly restore the air cushion to its original shape capable of absorb consecutive shocks.

[0017] It is still another object of the present invention to provide an air cushion for shock absorption, which can realize the discharge valve system and intake valve system of a simpler and easily controllable structure.

[0018] To achieve the above objects, there is provided an air cushion for shock absorption, the air cushion comprising a flexible foam material housed within a cover. The flexible foam material is explained by introducing a static force requirement, which is required to maintain the original size and shape thereof, and an impact force, which is operative when impacted. As already described above, the flexible foam material supporting a notebook computer of 6 pounds, for example, has the static force in excess of 6 pounds so as not to be transformed by the weight of the notebook computer. If the flexible foam material has 2 inches by 4 inches in a support surface thereof, the static force 6 pounds is dispersed into ¼ lb/in². In addition, the impact force applied to the notebook computer by a dropping becomes more than 50 times based on the calculated acceleration of gravity (G), whereby the notebook computer of 6 pounds produces an equivalent weight in excess of 300 pounds, and therefore the load force is dispersed into 12.5 lbim² or more.

[0019] As above, there happens actually greater difference between the static force requirement (¼ lb/in²) and the impact force (12.5 lbim²) of the flexible foam material. The present invention provides discharge valve means and intake valve means having different cross sectional area, respectively, in consideration of the difference of the static force requirement and impact force of the flexible foam material, whereby the respective valve means actively and alternatively respond to the impact force (300 pounds) and to the restoration force (6 pounds) needed to be restored to the shape under the static force.

[0020] The air cushion for shock absorption according to the present invention comprises: a flexible and elastic foam material capable of restoring an air cell thereof to its original shape and size under a static pressure transformable by an impact force; a cover made of a soft non-porous material for closely enclosing the foam material in the inside thereof; discharge valve means formed in the cover for discharging an air in the inside of the air cell of the foam material to the atmosphere when the air cell is subject to the shock; and one or more intake valve means formed in the cover, separately from the discharge valve means, for intaking the atmosphere to the air cell when the air cell is restored to its original size and shape after impacted.

[0021] The discharge valve means includes a porous portion in the cover to discharge an air in the inside thereof through extremely fine holes formed on the porous portion in the cover when shocked, whereby the first impact energy is efficiently absorbed by virtue of a conversion from a kinetic energy into a thermal energy in the process of the discharging. The intake valve means has a relatively greater volume in a cross sectional area thereof than the discharge valve means and is constructed a one-direction valve, which is closed when impacted but opened when restored, whereby the consecutive impact forces after the first impact can be efficiently absorbed by minimizing the difference between the pressure inside the air cushion and the atmosphere pressure and utilizing the restoration force (static force) of the flexible foam material almost without loss.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0023]FIG. 1 is a view of a conventional foam cushion installed inside a packing container;

[0024]FIG. 2 is a schematic view of another conventional air cushion installed inside a carrying case for a notebook computer or the like;

[0025]FIG. 3 is a detailed cross view of the air cushion of FIG. 2;

[0026]FIG. 4 is a detailed cross view of an essential part inside the air cushion of FIG. 3;

[0027]FIG. 5 is a cross view of an outer appearance of an air cushion according to the present invention;

[0028]FIG. 6 is a cross view of detached components of the air cushion according to the present invention;

[0029]FIG. 7 is a detailed view of a construction of discharge valve means in a gross cross section of the air cushion according to the present invention;

[0030]FIG. 8 is a detailed view of a construction of intake valve means in the gross cross section of the air cushion according to the present invention;

[0031]FIG. 9 is a view of an installation of the air cushion in a carrying case for a notebook computer according to the present invention;

[0032]FIG. 10 is a view of consecutive operations of the discharge valve means and intake valve means, when the air cushion is subject to an impact force and when the air cushion is restored, according to the present invention; and

[0033]FIG. 11 is a cross view of an air cushion for explaining discharge valve means according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

[0035] First, a preferred embodiment of the present invention will be described with reference to FIG. 5 to FIG. 8.

[0036] Referring to FIG. 5 to FIG. 8, an air cushion 20 for shock absorption according to the present invention comprises a flexible and elastic foam material 30 capable of restoring an air cell thereof to its original shape and size under a static pressure transformable by an impact force, and a film or fabric cover 40 made of a soft non-porous material for closely enclosing the foam material in the inside thereof. The foam material 30 is generally provided in the shape of block as shown in FIG. 5 to FIG. 8, despite no limit to its shape. The foam material 30 is a foam molding plastic material having either an opened cell or a closed cell. The foam material is preferably constructed an opened cell and has a minimum static force volume (stiffness needed to maintain shape), which is not transformable by a weight of a protected article including a notebook computer. The cover 40 is generally formed along the contour of the foam material 30 and encloses the foam material as closely as possible so as not to make any interstice between the foam material 30 and the cover 40.

[0037] Discharge valve means is provided in the cover 40 of the air cushion 20 according to the present invention for discharging the air inside an air cell of the foam material 30 when the air cushion is impacted, and one or more intake valve means are provided in the cover 40 of the air cushion 20 for intaking the atmosphere into the air cell when the air cell is restored to the original size and shape.

[0038] Preferably, the cover 40 is divided into two groups, one a lower cover 41 and the other an upper cover 42. The lower cover 41 is arranged to be contact with the bottom of the foam material 30, and the upper cover 42 covers other portions than the bottom of the foam material 30. Further, the lower cover 41 and the upper cover 42 are surrounded by flanges 43 and 44 as shown in FIG. 5 to FIG. 8, the respective flanges contact with each other. The flanges 43 and 44 are simply touched, not completely sealed to each other by the conventional fusion splicing method.

[0039] At the same time when the cover 40 is constructed, in the discharge valve means, a porous binder 50, for example, made of a textile fabric or a film is put on the mating flanges 43 and 44 to be stitched as shown in FIGS. 6 and 7. Referring to FIG. 6, the porous binder 50 is most folded along the contour of the flanges in the cover but partially unfolded. Actually, one unfolded textile fabric or film is prepared, the top surface and bottom surface of the flanges 43 and 44 are folded and stitched, and finally both ends of the textile fabric or film are put on one after another and stitched as shown in FIG. 7. In the discharge valve means comprising the porous binder 50, if the air cushion is compressed by a shock, an air contained in the air cell of the flexible foam material 30 is passed through the interstice 45 between the mating flanges 43 and 44 and discharged through fine holes 53 formed in the flanges and the porous material 50, which are formed when a suture is penetrated through the fine holes 53 formed in the flanges 43 and 44 and porous material 50 to stitch the fine holes originally present in the porous material 50, the flanges 43 and 44 and the porous material 50.

[0040] The intake valve means is manufactured in one-direction, so that it is closed when the shock is applied to the air cushion whereas it is opened when the air cushion is restored. The gross cross sectional area of the intake valve means for air communication is designed to be greater than the gross cross sectional area of the fine holes in the discharge valve means for air communication. This is because, above all, the intake valve means are maintained to be closed when the air cushion is subject to the shock, and thus the internal air can be discharged through a restricted volume of passages. Since the air discharge velocity is increased at a fixed rate corresponding to the increase of the impact force, a dynamic (active) control capacity is produced appropriate to each impact condition from small to great. If the cross sectional area of the discharge valve means is extremely large, air discharge resistance does not occur and the transformation of the air cushion is dependant on only stiffness of the foam material 30, failing to sensitively respond to the size of the impact force and efficiently absorb the impact force. Second, since the atmosphere from outside is easily intaked without air resistance through the intake valve means having the greater cross sectional area when the air cushion after impacted is restored to its original size and shape, the air cushion is promptly restored and thus absorbs consecutive shocks following the first shock with ease.

[0041] Here, the cross sectional area of the discharge valve means is decided depending on fineness of the material for the porous binder 50 and stitch interval when the binder 50 is stitched. For instance, if the fineness of the material for the binder 50 is great, air communication volume becomes small, whereas if the stitch interval is narrow, namely the number of stitches is great, the number of holes through which the suture is passed is increased, thereby increasing the air communication volume.

[0042] Preferably, in the intake valve means, the lower cover 41, namely, the bottom of the cover 40, is of a flat structure and includes an opening 47 thereon and a valve plate 60 for opening and closing the opening 47. The valve plate 60 is made of a soft non-porous film or textile fabric, preferably PVC, and covers the opening 47 in the inner bottom of the lower cover 41. One end of the valve plate 60 is secured to the bottom of the lower cover 41 by means of a bonding or a fusion splicing, and other freely moved ends of the valve plate 60 open and close the opening 47 by vertically moving. While the valve plate 60 is closely attached to the bottom of the cover 40 due to a positive pressure inside the air cushion generated when the air cell is compressed by the shock, thereby closing the opening 47, the freely moved ends of the valve plate 60 are detached from the bottom of the lower cover 41 by a negative pressure generated inside the air cushion 20 when the compressed air cell is restored to the original size and shape, thereby opening the opening 47. Further, the flexible foam material 30 has a receiving recess 31 in the bottom thereof for providing a room appropriate to the vertical open-and-close operation of the valve plate 60.

[0043]FIG. 9 is a view of a preferred installation of the air cushion 20 constructed as above in a carrying case for a notebook computer.

[0044] Referring to FIG. 9, the air cushion 20 for shock absorption is installed in the carrying case in the same state as in the carrying case 5 of FIG. 2. The air cushion 20 includes two independent blocks, namely, a first cushion 20 a and a second cushion 20 b. The first cushion 20 a for supporting the weight of the notebook computer at the bottom of the carrying case and the second cushion 20 b for pressing a lateral face of the notebook computer to a lateral face of the carrying case are connected with each other.

[0045] A support plate 70 indicated at 70 is provided to prevent the air cushion structure from being arbitrarily transformed when the air cushion is installed in the carrying case and facilitate the installation of the air cushion, similarly in FIG. 2. It should be notified that the surface of the support plate 70 is preferably made of cotton fabric, cotton knit, or similar porous fiber. Since the surface of the support plate 70 is made of that kind of fiber, the opening 47 of the intake valve formed in the bottom of the air cushion is not closed when the air cushion is pressed, enabling the air to be communicated.

[0046]FIG. 10 is a view of an operation of the air cushion 20 according to the present invention.

[0047] Referring to FIG. 10, the top air cushion shows the static force state, the intermediate air cushion shows the transformation state when impacted, and the bottom air cushion shows the restoration state.

[0048] First, in the static force state as shown at the top air cushion, since the air inside the cover 40 is operative through the fine holes on the porous binder 50, the article, such as the notebook computer, housed in the case is bolstered based on the stiffness of the foam material 30. Here, the valve plate 60 is naturally attached to the bottom of the lower cover 41, closing the opening 47.

[0049] Next, if the air cushion is subject to the shock due to a dropping of the carrying case or the like as shown in the intermediate air cushion, the foam material 30 is compressed, the pressure inside the cover 40 rises, and then the valve plate 60 is closely contact with the bottom of the lower cover by the increased pressure, resulting in the closure of the opening 47. Therefore, the air inside the air cushion 20 at the increasing pressure can be released to the atmosphere only through the fine passages on the material for the porous binder 50. Since the passages on the porous binder 50 form too limited fine ways for airing, the discharge velocity becomes faster when the impact force is greater whereas the discharge velocity becomes slower when the impact force is smaller. The first impact force is absorbed in the above course.

[0050] Next, once the first shock is eliminated as shown in the bottom air cushion, the compressed foam material 30 is forced to be restored to the original size and shape by the pre-determined static force. When the foam material 30 commences to be restored, the negative pressure occurs inside the cover 40 and is operative to absorb the air from the outside. Here, since the fine air passages on the porous binder 50 being in communication with the atmosphere in the above described process when impacted have less volume thereof, the air can not be smoothly entered through the fine air passages by only means of the mere restoration force of the flexible foam material 30. Accordingly, the negative pressure generated inside the cover 40 is operative to the valve plate 60, thereby detaching the freely moved ends of the valve plate 60. Once the valve plate 60 is detached, the opening 47 is opened, whereby the air enters into the inside from the outside. In this event, since the opening 47 is set to be a greater volume according to the present invention, the opening does not adversely affect the air passed therethrough, and since the air can be intaked in great quantity at the same time, the restoration operation is fast carried out, thereby being quickly restored to the state capable of absorbing the following shocks. If the valve plate 60 moves up and the opening 47 is opened, almost air will be intaked through the opening 47, not through the fine air passages on the binder 50.

[0051] According to another embodiment of the present invention, the soft nonporous valve plate 60 can be replaced by the porous film. Here, the porous valve plate functions as not only the intake valve means but also another discharge valve. Therefore, the air inside the air cushion 20 is discharged through the fine holes on both porous binder 50 and porous valve plate when the impact force is operated. But, if the valve plate is detached and the opening is opened when restored, the fine holes on the valve plate rarely function as the air passages, and thus the opening is used for the most air to be communicated.

[0052]FIG. 11 is a cross view of an air cushion for explaining discharge valve means according to another embodiment of the present invention.

[0053] In the discharge valve means 40 already described in the above, the cover 40 is divided into two groups, the lower cover 41 and the upper cover 42, the flanges 43 and 44 of the lower cover 41 and upper cover 42 are simply contact with each other, and the mating flanges 43 and 44 are stitched to the porous binder 50.

[0054] Contrarily, in the air cushion 200 according to another embodiment of the present invention, one portion of a lateral face of a non-porous cover 80 is a porous part 90. The cover 80 is made of a non-porous film or textile fabric, maintaining a complete sealing state. Referring to FIG. 11, even if the cover is divided into a lower cover 81 and an upper cover 82 both having flanges 83 and 84 as like in the first embodiment of the present invention, the flanges 83 and 84 are completely sealed by a bonding, fusion splicing, or the like, and one portion of the sealed cover 80 is the porous part 90. Here, it is not necessarily observed that the cover 80 is divided into the lower cover 81 and the upper cover 82.

[0055] The porous part 90 may be made by forming a plurality of fine holes in communication with the atmosphere at the one portion of the lateral face of the cover 80 itself, or by cutting an area on the cover 80 to make an opening 85 and attaching a valve plate 91 materialized of a porous film, textile fabric, or the like to the opening as shown in FIG. 11.

[0056] According to still another embodiment of the present invention, not drawn in any FIGs, the discharge valve means does not include the binder 50 or the valve plate 91 as like in the above embodiments but includes a cover materialized of a porous film, textile fabric, or the like, so that the cover itself acts as the discharge valve without any additional discharge valve means.

[0057] Meanwhile, in case that the cover includes the lower and upper covers, at least one of them is made of a porous material. That is, both lower cover and upper cover may be of the porous material, the lower cover only may be of the porous material, or the upper cover only may be of the porous material.

[0058] As stated above, the air cushion for shock absorption according to the present invention basically comprises the porous discharge valve and the intake valve. Since the compressed air inside is discharged through the discharge valve having the volume extremely restricted by the porous material, the air discharge velocity is dependent on the size of the impact force, efficiently attenuating the impact force. Furthermore, since the air is intaked through the intake valve having the relatively great volume, the air resistance becomes extremely low, whereby all the static force pre-applied to the foam material functions as the restoration force. Accordingly, the air cushion can be more promptly restored and efficiently absorb the following shocks.

[0059] Finally, according to the present invention, when shocked or restored, the shock can be efficiently absorbed by selectively operating the discharge valve and intake valve and differing their volumes from each other. Thus, the articles, for example notebook computer, which are easily broken and damaged in performance, can be more perfectly protected.

[0060] Moreover, the present invention does not employ the conventional check valve, pressure adjusting valve, or the like, which is structurally complicated in terms of the mechanics, electronics, or the like and has difficulty in being adapted to the air cushion, but employs the air cushion materialized of the film, textile fabric, or the like, which is structurally simple, and possibly self-controlled, without affecting the original function of the air cushion as well as reducing the cost.

[0061] While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 

What is claimed is:
 1. An air cushion for shock absorption comprising: a flexible and elastic foam material capable of being restored to its original shape and size under static pressure after being subjected to an impact force; a cover made of a soft non-porous material for closely enclosing and sealing the foam material; at least one discharge valve formed in the cover for discharging air in the inside of the air cells of the foam material to the atmosphere when the air cushion is impacted; and at least one intake valve formed in the cover for intaking the atmosphere to the air cells when the air cushion is restored to its original size and shape after being impacted.
 2. The air cushion of claim 1, wherein the cover is divided into an upper cover and a lower cover, each of which has flanges surrounding ends thereof, the discharge valve comprising a porous binder on the mating flanges, the atmosphere and the inside of the air cushion being in communication with each other through fine holes formed in the flanges and porous binder, which are formed when a suture is used to stitch the mating flanges, the fine holes being originally formed in the porous binder and the flanges.
 3. The air cushion of claim 1, wherein the discharge valve comprises a porous part in one portion of a lateral face of the cover.
 4. The air cushion of claim 3, wherein the porous part in the one portion of the lateral face of the cover includes a plurality of fine holes.
 5. The air cushion of claim 3, wherein the porous part is formed by cutting an area on the cover and attaching an additional porous material to the cut portion.
 6. The air cushion of claim 1, wherein the intake valve is constructed as a one-way valve, which is closed when the air cushion is subject to the shock but opened when the air cushion is restored.
 7. The air cushion of claim 1, wherein the intake valve comprises: an opening formed in the bottom of the cover; a valve plate attached to the internal bottom of the cover at one end thereof for vertical movement depending on a difference between the pressure inside the air cushion and the atmospheric pressure to open or close the opening; and a recess formed in a bottom of the flexible foam material for receiving a valve plate, the recess providing appropriate space for the vertical open-and-close operation of the valve plate.
 8. The air cushion of claim 7, wherein the valve plate is made of a soft nonporous material, and wherein the valve plate is in close contact with the bottom of the cover due to a positive pressure generated inside the air cushion when the air cushion is compressed by a shock, thereby closing the opening, whereas a freely moving end of the valve plate is detached from the bottom of the cover due to a negative pressure generated inside the air cushion when the compressed air cushion is restored to its original size and shape, thereby causing the opening to allow the passage of air into the air cushion.
 9. The air cushion of claim 7, wherein the valve plate discharges internal air to the outside, through fine holes originally formed in the valve plate material itself, when the foam material is shocked by closing the opening due to the internal pressure generated, and the valve plate intakes the atmosphere to the air cushion through the opening when the flexible foam material is restored to its original size and shape by forcing open the opening when the freely moving end thereof is detached from the bottom of the lower cover due to the difference between a negative pressure generated inside and an atmosphere pressure.
 10. The air cushion of claim 1, wherein the cross sectional area of the intake valve for air communication is greater than the cross sectional area of the discharge valve for air communication.
 11. An air cushion for shock absorption comprising: a flexible and elastic foam material capable of being restored to its original shape and size under a static pressure but being transformable by an impact force; a cover made of a soft porous material for closely enclosing the foam material and functioning as an air discharge valve in communication with the inside of the air cushion and the atmosphere through fine holes formed in the porous material; and one or more intake valves formed in the cover for intaking the atmosphere into the air cushion when the air cushion is restored to its original size and shape.
 12. The air cushion of claim 11, wherein the cross sectional area of the one or more intake valves for air communication is greater than the cross sectional area of the discharge valve.
 13. The air cushion of claim 11, wherein the air cushion includes a support member attached to an outer face of the lower cover for supporting the air cushion structure, the surface of the support member being made of a porous fiber for achieving smooth air communication through the opening of the intake valve on the lower cover.
 14. An air cushion for shock absorption comprising: a flexible and elastic foam material capable of being restored to its original shape and size under a static pressure after being subjected to an impact force; a cover divided into a lower cover in close contact with a bottom of the foam material, and an upper cover attached to the lower cover and closely covering portions other than the bottom of the foam material, at least one out of both covers made of a soft porous material for functioning as an air discharge valve in communication between the air cushion and the atmosphere through fine holes formed in the porous material; and one or more intake valves formed in the lower cover for intaking the atmosphere into the air cushion when the air cushion is restored to its original size and shape after being subjected to the shock force, wherein the intake valve comprises an opening formed in a bottom of the lower cover, a valve plate attached to an internal bottom of the cover at one end thereof and made of a soft material for opening and closing the opening by virtue of a vertical movement of the other freely moving end thereof, and a valve plate receiving recess formed in the bottom of the flexible foam material for providing appropriate room for the vertical open-and-close operation of the valve plate.
 15. The air cushion of claim 14, wherein the cross sectional area of the intake valve for air communication is greater than the cross sectional area of the discharge valve for air communication.
 16. The air cushion of claim 14, wherein the air cushion includes a support member attached to an outer face of the lower cover for supporting the air cushion structure, the surface of the support member being made of a porous fiber for achieving smooth air communication through the opening of the intake valve on the lower cover.
 17. An air cushion for shock absorption comprising: a flexible and elastic foam material capable of being restored to its original shape and size under a static pressure but being transformable by an impact force; a cover made of a soft non-porous material for completely sealing the foam material; one or more intake valves formed in a lower cover for intaking the atmosphere into the air cushion when the air cushion is restored to its original size and shape after being subjected to an impact force; wherein the cover is divided into the lower cover in close contact with a bottom of the foam material, and an upper cover fusion spliced on a top of the lower cover for closely enclosing portions other than the bottom of the foam material, wherein the one or more intake valves comprise an opening formed in a bottom of the lower cover, and a valve plate attached to an internal bottom of the cover at one end thereof for opening and closing the opening by virtue of a vertical movement of a freely moving end thereof, and a valve plate receiving recess formed in the bottom of the flexible foam material for providing room appropriate for the vertical open-and-close operation of the valve plate, wherein the valve plate is made of a porous material for discharging internal air to the outside, through fine holes originally formed in the valve plate material itself, when the foam material is shocked by closing the opening due to the internal pressure generated, and for intaking the atmosphere to the air cushion through the opening when the flexible foam material is restored to its original size and shape by opening the opening when the freely moving end thereof is detached from the bottom of the lower cover due to the difference between a negative pressure generated inside and an atmosphere pressure.
 18. The air cushion of claim 17, wherein the cross sectional area of the intake valve is greater than the cross sectional area of the discharge valve.
 19. The air cushion of claim 17, wherein the air cushion includes a support member attached to an outer face of the lower cover for supporting the air cushion structure, a surface of the support member made of a porous fiber for achieving smooth air communication through the opening of the intake valve on the lower cover.
 20. An air cushion for shock absorption comprising: at least one shock-absorbing member, wherein the shock-absorbing member comprises a porous material having interstices for receiving air, wherein the porous material is capable of being deformed by an impact force, and wherein the material is capable of being restored to its original shape and size after being subjected to the impact force; a cover for enclosing the shock-absorbing member, wherein the cover is made of a nonporous material; at least one air discharge valve, formed in the cover, for discharging air from the shock-absorbing member into the atmosphere when the air cushion is subjected to an impact force; at least one air intake valve, formed in the cover, for allowing air to pass from the atmosphere into the inside of the cover for filling the interstices of the shock-absorbing member, thereby restoring the shock-absorbing member to its original size and shape after the shock-absorbing member has been subjected to an impact force; and wherein the at least one air intake valve is a one-way valve. 